The present invention relates to a device for injecting a measured amount of fertilizer beneath the surface of the soil.
It is desirable to place fertilizer beneath the surface of the soil when fertilizing garden plants, trees and shurbs, due to the fact that when placed on the soil surface, rainfall and watering can prematurely wash the fertilizer away. By placing the fertilizer beneath the soil, the root system will absorb the nutrients more quickly and efficiently and the fertilizer will not become weakened as it is filtered from the surface of the soil to the root system.
Tilling the soil is an effective way to distribute the fertilizer properly, but this is a laborious and time consuming task and is not always practical. A thick stand of shrubs, for example, cannot be tilled because the root system might be damaged and because soil at the base of the shrub is inaccessible as a result of the thick foliage.
Several patents have been issued for devices which inject fertilizer beneath the surface of the soil, for example U.S. Pat. No. 3,504,647 to Krarup discloses a fertilizer applicator comprised of a frusto-conical hopper with an aperture at the bottom and center of the hopper and a dibble rod mounted in the center of the hopper and a support rod attached to the cone shaped bottom of the hopper.
Another fertilizer injector is disclosed in U.S. Pat No. 2,370,744 to Molinare. In this patent is also disclosed a frustro-conical hopper with an aperture and injector rod centrally located therein.
A more complex fertilizer injector is disclosed in U.S. Pat. No. 3,014,443 to Keyser et al. This patent also has a funnel shaped hoppeer with an aperture and injector rod centrally located in the hopper.
Another device which could be used for injecting fertilizer is described in U.S. Pat. No. 3,815,526 to Christopherson. In this patent, the hopper is a tubular barrel with an outlet at the bottom and contains a centrally located valve rod.
Although all of these inventions are meritorious, they contain certain deficiencies which the present invention will overcome. For example, the Krarup device (U.S. Pat. No. 3,504,647) discloses two vertically extending rods, a dibble rod and a stationary supporting rod. Both rods are shaped in the form of an inverted "L". This would allow a force to be applied to only one side of each rod, thus the dibble rod would have a tendency to bind in its travel through the guide collars mounted on the support rod when it is manually raised and lowered. Another deficiency is the mounting of the vertical support rod. The support rod is mounted to one side of the axis of the hopper and it is attached to the hopper only at one place on the bottom of the cone shaped portion of the hopper. In this arrangement when the hopper is full of fertilizer and is lifted by the handle of the support rod, which is also off center, the weight of the load would be off balance, tending to rotate counter clockwise about the handle. Thus the user in order to balance the load would have to exert a torque force to overcome the offset center of gravity as well as the force to lift the weight contained in the hopper. A further deficiency in this design is that after repeated use, the material of the hopper would have a tendency to fail at the small area where the support rod is attached to the hopper. Still a further deficiency in the design is that in order to fill the bore hole with fertilizer, the dibble rod handle is pulled up and must overcome a spring force, as the offset support rod is pushed down. In this action an upward force is applied to a guide collar attached to the support rod approximately a third of the way down from the handle of the support rod, and a downward force is applied to the bottom of the support rod where it is attached to the hopper. Since these two forces are not in the same axis, but both act on the support rod, a moment arm is created which tends to cause the bottom of the support rod to rotate about the guide collar. Thus, if there were not sufficient weight in the hopper it would pull laterally away from the bore hole. Also, the hopper is open at the top which would allow leaves, twigs and other foreign material to enter the hopper and impede the gravitational flow of fertilizer.
The Molinare invention (U.S. Pat. No. 2,370,744 ) is a simple device, but also has certain deficiencies. For example, if the device is to be used by a person in a standing position and if the finger operated latch is close to the handle and at the top of the hopper it becomes necessary to provide a long reciprocating rod. When the hopper is filled, the entire length of the reciprocating rod is in contact with the fertilizer causing a great deal of friction on the rod. The user must overcome a large frictional resistance to move the rod up and down. Another deficiency in the Molinare device is seen when forming a hole in the soil. When the cone shaped valve member is in the up position it is retracted into a cone shaped portion of the chambered body which forms a port or hole. When the device is pressed into the soil, the port or hole in the cone shaped chamber would fill with soil and prevent the cone shaped valve member from projecting outwardly beyond the lower end of the chambered body. A further deficiency is seen when granular material flows from the spout of the tubular portion of the hopper into the measuring chamber. After the measuring chamber has filled with granular material the rod is lifted up causing the valve element to seal off the spout. However, the upward lift would compact the granular material and cause it to be jammed in the down position. A still further deficiency in the Molinare device is that it makes no provision for selectively measuring a quantity of fertilizer.
The Keyser et al U.S. Pat. No. (3,014,443 ) is a rather complex device having a large number of parts which would make it undesirable for economical manufacture. Inside the square shaped hopper is a disc with an arcuate slot sandwiched between an upper plate having an arcuate slot and a lower plate having an arcuate slot and a series of holes. The fertilizer must pass through these slots and holes to be dispersed. This arrangement could easily become clogged and unworkable if a large lump of fertilizer were to enter and plug one of the slots or holes. Another deficiency in the Keyser device is that in order to vary the amount of fertilizer to be dispersed, it is necessary to change the disc. To do this would require the user to dis-assemble the device.
The Christopherson U.S. Pat. No. (3,815,526) is designed to inject rodent poison underground. However, it could be used to inject fertilizer as well. Several deficiencies are noted in this device also. For example, the hopper consists of an elongated outer barrel, with an elongated rod disposed axially within the barrel. The rod must be moved up and down through the granular material to measure out a certain amount of the material. However, this up and down movement would be difficult due to the friction of the granular material on the length of the rod. Another deficiency in the Christopherson patent is that to fill the device, the top of the barrel is unscrewed and the rod is removed from the barrel. With the bottom open end or port of the barrel held against the ground the barrel is filled with a premeasured amount of granular material. To do this, the user must hold the barrel perfectly straight with one hand while filling it with the other hand. This would be difficult to do if the material used to fill the barrel was in a bag type container. In most instances the user would prop the barrel against a stationary object and use both hands for filling. This means that the granular material would flow out the open bottom end of the barrel. A further deficiency in the Christopherson device is that after the barrel is filled, the rod is inserted into the barrel until the end of the rod closes the open bottom end of the barrel. This means that the rod must push through an elongated section of granular material thusly building up more and more friction the farther it is pushed down into the granular material. Also, there is no provision for guiding the rod on its downward path, other than the side walls of the barrel. Therefore it would be difficult to get the rod into the center of the barrel without several attempts using only one hand. Also, as the rod is pushed down, it would force more granular material out the end of the barrel. Thus a large portion of the granular material would be wasted during the filling operation.
None of the aforementioned patents make provision for filtering out large chunks of the granular fertilizer that form in storage as a result of dampness or high humidity conditions. Nor do any of the patents provide for offsetting the injector rod from the center of the hopper so that the injector rod has to displace a minimum amount of fertilizer as it travels up and down and thereby cutting down on friction on the injector rod.